Curable compositions

ABSTRACT

1. A FLUID COMPOSITION STABLE UNDER SUBSTANTIALLY ANHYDROUS CONDITIONS AND CURABLE TO AN ELASTIC SOLID IN THE PRESENCE OF MOISTURE CONSISTING ESSENTIALLY OF A BASE SILANOL CHAIN-STOPPED POLYDIORGANOSILOXANE HAVING THE FORMULA,   H-(O-SI(-R10)(-R11))Q-OH   WHERE R10 AND R11 ARE INDEPENDENTLY SELECTED FROM THE CLASS CONSISTING OF HYDROCARBYL, HALOHYDROCARBYL AND CYAND LOWER ALKYL AND Q VARIES FROM 300 TO 5,260, A SILANE REPRESENTED BY THE FORMULA:   RMSI(OR1)4-M   0.01 TO 10 PARTS BASED ON 100 PARTS OF THE BASE POLYDIORGANOSILAXANE OF A TITANIUM CHELATE CATALYST AND 0.3 TO 20 PARTS BASED ON 100 PARTS OF THE POLYDIORGANOSILOXANE OF A VISCOSITY DEPRESSANT OF THE FORMULA:   HO-(SI(-R4)(-R5)-O)P-H   WHEREIN R IS A RADICAL HAVING NOT MORE THAN ABOUT 8 CARBON ATOMS SELECTED FROM THE GROUP CONSISTING OF HYDROCARBYL, HALOHYDROCARBYL, AND CYANO LOWER ALKYL, R1 IS A RADICAL NOT HAVING NOT MORE THAN ABOUT 8 CARBON ATOMS SELECTED FROM THE GROUP CONSISTING OF HYDROCARBYL, HALOHYDROCARBYL AND CYANO LOWER ALKYL, R4 AND R5 ARE EACH ORGANIC RADICALS OF NOT MORE THAN 8 CARBON ATOMS SELECTED FROM THE GROUP CONSISTING OF HYDROCARBYL, HALOHYDROCARBYL AND CYANO LOWER ALKYL, M HAS A VALUE OF 0 TO 3 AND AN AVERAGE VALUE BASED UPON THE TOTAL AMOUNT OF SILANE IN THE COMPOSITION OF 0 TO 1.99, AND P HAS A VALUE OF 2 TO 46.

United States Patent 3,845,161 CURABLE COMPOSITIONS Melvin D. Beers,Ballston Lake, N .Y., assignor to General Electric Company No Drawing.Continuation-impart of application Ser. No.

267,192, June 28, 1972, which is a continuation-inpart of applicationSer. No. 153,812, June 16, 1971, both now abandoned. This applicationSept. 26, 1973, Ser. No. 400,895

Int. Cl. C08g 47/02 US, Cl. 260-825 Claims ABSTRACT OF THE DISCLOSUREFluid organopolysiloxanes which are vulcanizable at room temperature tosilicone elastomers are prepared by mixing a titanium chelate catalyst,a cross-linking agent such as methyltrimethoxysilane, a silanolchain-stopped polydiorganosiloxane fluid having a viscosity of fromabout 1,000 to about 10,000,000 centipoise at 25 C., and a low molecularweight silanol-stopped polydiorganosiloxy fluid which acts as aviscosity depressing additive in the absence of moisture. Thesecompositions are stable, free-flowing fluids in the absence of moisturebut cure to the rubbery solid, elastic state upon exposure to moisture.The compositions are particularly useful as adhesives and sealants inthe construction of electronic equipment in that they do not give offcorrosive by-products when curing. They are also useful in the formationof orthopedic devices cast on the human foot.

BACKGROUND OF THE INVENTION This application is a continuation-in-partof parent application Ser. No. 267,192, filed June 28, 1972, which is acontinuation-in-part of parent application Ser. No. 153,812, filed June16, 1971 of Melvin D. Beers, both now abandoned.

This invention pertains to a viscosity depressing additive for fiuidorganopolysiloxanes which are capable of vulcanizing at room temperatureto rubbery materials.

The prior art room temperature vulcanizing materials (RTVs) comprise alinear polymer and a cross-linking agent. The prior art alkoxy type ofnon-corrosive RTVs which have had commercial success have suffered thedisadvantage of extreme thickening during the initial mixing of theingredients due to the presence of the titanium chelate catalystfollowed by a viscosity decrease only upon prolonged standing. Adisadvantage of the RTVs which thicken immediately upon mixing theingredients is that it is difiicult to handle the material in itsthickened state, thus making the mixing, transferring and packagingsteps burdensome.

SUMMARY OF THE INVENTION The RTVs of the present invention comprise abase silanol chain-stopped polydiorganosiloxane having a viscosity ofpreferably from about 1,000 to 90,000 centistokes and generally of 1,000to 10,000,000, centistokes at 25 C., at least one silane represented bythe formula:

1 -R Si(OR and a titanium chelate catalyst, preferably a titaniumchelate catalyst of the formula:

2 x w k (2) R 0 /T| 7 0 \A/ O C and a viscosity depressant of theformula:

HO S IiO+H where R is a radical having not more than about 8 carbonatoms selected from the group consisting of hydrocarbyl,halohydrocarbyl, and cyano lower alkyl where the hydrocarbyl radicalsmay have carboxy moieties therein, R is a radical not having not morethan about 8 carbon atoms selected from the group consisting ofhydrocarbyl, halohydrocarbyl and cyano lower alkyl, R is a radicalselected from the group consisting of hydrogen, hydrocarbyl having notmore than about 8 carbon atoms, carboxyalkyl and halohydrocarbyl havingnot more than about 8 carbon atoms and the total number of carbon atomsin the R and R substituted alkanedioxy radical is not more than about18, R is a radical having not more than about 8 carbon atoms selectedfrom the group consisting of hydrocarbyl, halohydrocarbyl and cyanolower alkyl, R and R are each organic radicals of not more than 8 carbonatoms selected from the group consisting of hydrocarbyl, halohydrocarbyland cyano lower alkyl, p varies from 2 to 46, generally, and preferablyvaries from 3 to 9, R can be selected from the same group as R and, inaddition, can be halo, cyano, nitro, carboxy ester, acyl and hydrocarbylsubstituted by halo, cyano, nitro, carboxy ester and acyl, R is selectedfrom the group consisting of hydrogen, hydrocarbyl having not more thanabout 8 carbon atoms, halohydrocarbyl having not more than about 8carbon atoms, acyl having not more than about 8 carbon atoms, and takentogether with R can form together with the carbon atoms to which theyare attached cyclic hydrocarbon substituents of not more than about 12carbon atoms and chloro, nitro, acyl, cyano and carboxy estersubstituted cyclic hydrocarbon substituents; X is a radical selectedfrom the class consisting of radicals having up to about 20 carbon atomsselected from the group consisting of hydrocarbyl, halohydrocarbyl,cyanoalkyl, alkoxy, haloalkoxy, cyanoalkoxy and amino, a has a value of0 to 8 and such that when a is zero the moieties are bonded to eachother in a cyclic fashion, In has a value of 0 to 3 and an average valuebased upon the total amount of silane in the composition of 0 to 1.99.

The term hydrocarbyl as used here means the hydrocarbon from which onehydrogen atom has been removed, i.e., a monovalent hydrocarbon radical.

The abbreviation of RTV as used herein means a room temperaturevulcanizable material.

In the construction and fabrication of electronic components the mixingimmediately prior to using requirements, the corrosion problems and thethickening and thinning with time problems associated with the prior artRTVs no longer exist. The #RTVs of the present invention do not requiremixing immediately prior to use, are stable indefinitely, do not thickenappreciably upon mixing the ingredients, and do not result in corrosionwhen used in electronic circuits. They are also useful in thefabrication of orthopedic devices which can be cast and cured on thehuman foot or other body member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the formula of thecross-linking agent used in the practice of the present invention IR andR can be, for example, mononuclear aryl, such as phenyl, benzyl, tolyl,xylyl and et-hylphenyl; halogensubstituted mononuclear aryl, such as2,6-di-chlorophenyl, 4 brornophenyl, 2,5-di-fluorophenyl, 2,4,6trichlorophenyl and 2,5 di'bromophenyl; alkyl such as methyl, ethyl,n-propyl, is-opropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, amyl,hexyl, heptyl, octyl; alkenyl such as vinyl, allyl, n-butenyl-l,n-butenyl-2, n-pentenyl-Z, nhexenyl-2, 2,3 dimethylbutenyl 2,n-heptenyl; alkynyl such as propargyl, Z-butynyl; haloalkyl such aschloromethyl, iodomethyl, brornomethyl, fiuoromethyl, chloroethyl,iodoethyl, bromoethyl, fiuoroethyl, trichloromethyl, di-iodoethyl,tribrom-omethyl, trifluoromet'hyl, dichloroethyl, chloro-n-propyl,bromo-n-propyl, iodoisopropyl, bromo n b-utyl, bromo-tertbutyl,1,3,3-trichlorobutyl, 1,3,3 tribromobutyl, chloropentyl, bromopentyl,2,3-dichloropentyl, 3,3 di'bromopentyl, chlorohexyl, bromohexyl, 1,4d'ichlorohexyl, 1,3 dibromohexyl, bro mooctyl; haloalkenyl such aschlorovinyl, bromovinyl, chloroallyl, bromoallyl, 3 chloro n butenyl 1,3- ehloro-n-pentenyl 1, 3 fluoro n heptenyl-l, 1,3,3- trichloro nhepte-nyl 5, 1,3,S-trichloro-n-octenyl-6, 2,3,3 trichloromethylpentenyl4; haloalkynyl such as chloropropargyl, bromopropargyl; cycloalkyl,cycloakenyl, and halogen-substituted cycloalkyl and cycoalkenyl such ascyclopentyl, cyclohexyl, cyclohepteyl, cycl'ooctyl, 6-methylcycl-ohexyl, 3,4 dichlorocyclohexyl, 2,6-dibromocycloheptyl, 1cyclopentenyl, 3 methyl 1 cyclo pentenyl, 3,4 dime'thyl 1 cyclopentenyl,S-methyl-S- cyclopentenyl, 3,4 dichloro 5 cyclopentenyl, S-(tertbutyl) 1cyclopentenyl, l-cyclohexenyl, 3-methyl-1- cyclohexenyl, 3,4 d-imethyl 1cyclohexenyl; and cyano lower alkyl such as cyanomethyl,beta-cyanoethyl, gamma cyanopropyl, delta cyan-obutyl, andgammacyanoisobutyl.

In the formula of the preferred catalyst used in the practice of thepresent invention R can be hydrocarbyl and hal'ohydrocarbyl such asthose listed above for R or hydrogen. In addition, R can be a carboxyalkyl of the formula R CO where R is selected from the same group as Rand can be joined to the CO group either through the carbonyl carbon oran oxygen atom of the carboxyl group, R can be hydrocarbyl,halo-hydrocarbyl and cyanoalkyl such as those listed above for R, R is aradical having not more than about 8 carbon atoms and can be selectedfrom the same group as R and, in addition, can be halo, cyano, nitro,oarboxy ester, acyl and substituted hydrocarbyl containing halo, cyano,nitro, c'arboxy ester and acyl, the substituted hydrocarbyl can bederived from those listed above for IR and the hydrocarbyl portion ofthe carboxy ester and the acyl can also be selected from the hydrocarbyllisted above for R, R is selected from the group consisting of hydrogen,hydrocarbyl having not more than about 8 carbon atoms selected from thegroup set forth in the definition of R, halohydrocarbyl having not morethan about 8 carbon atoms selected from the group set forth in thedefinition of R, acyl having not more than about 8 carbon atoms, thehydrocarbyl portion of which is selected from the group set forth in thedefinition of R. In addition, R' when taken together with R can formtogether with the carbon atom-s to which they are attachedcyclohydrocarbon subst-ituents of not more than about 12 carbon atomsand chloro, nitro, acyl, cyano and carboxy ester substitutedcyclohydrocarbon substituents,

the hydrocarbyl portion of the carboxy ester and acyl can be selectedfrom the hydrocarbyl listed above for R, X can be hydrocarbyl,halohydrocarbyl and cyanoa'lkyl such as those listed above for R. Inaddition, X can be a radical having up to 20 carbon atoms selected fromthe group consisting of alkoxy, haloalkoxy, and cyanoalkoxy and amine.The groups represented by X can be methoxy, ethoxy, butoxy, propoxy,pentoxy, heptoxy; haloalkoxy such as chloromethoxy, iodomethoxy,bromomethoxy, fluoromethoxy, chloromethoxy, iodoethoxy, bromoethoxy,fluoroeth-oxy, tri-chloromethoxy, diiodoethoxy, dibromomethoxy,trifluromethoxy, d'ichloroethoxy, chloro n propoxy, brorno-n-propoxy,iodoisopropoxy, bromo n butoxy, bromo-tert-butoxy, 1,3,3-trichlorobutoxy, 1,3,3 tribrom-obutoxy, chloropentoxy, bromopentoxy, 2,3dichloropentoxy, 3,3 dibromopentoxy, chlorohexoxy, bromohexoxy, 2,4dichlorohexoxy, 1,3 dibromohexoxy, 1,3,4 trichlorohexoxy, chlorohexoxy,c-hloroheptoxy, bromoheptoxy, iiuoroheptoxy, 1,3 dichloroheptoxy, 1,4,4trichloroheptoxy, 2,4- dichloromethylheptoxy, chlorooctoxy,brom-ooctoxy, iodooctoxy, 2,4 dichloromethylhexoxy, 2,4 dichlorooctoxy,2,4,4 trichloromethylpentoxy, 1,3,5 tribromooctoxy; the cyanoalkoxy canbe cyan'omethoxy, betacyanoethoxy, gamma-cyanopropoxy, deltacyanobutoxy, gamma cyanoisobu-toxy, beta cyanopropoxy andalphacyanobutoxy; the hydrocarbyl portions of the amino can be selectedfrom the group defined by R and the amino can be, for example,diethylamino, methylamino, diiso propylamino, oc-tylamino, andethylbutylamino. Although in many applications of the first roomtemperature vulcanizable silicone rubber compositions of the presentcase, in the chelate catalyst used therein X may have up to 8 carbonatoms, in some applications of the first room temperature vulcanizablesilicone rubber compositions especially in the insulation of electricalcomponents Where essentially no corrosive by-products are desired in thecure of the compositions it is preferred that in the chelate catalyst Xhave up to 2 to 20 carbon atoms such as 15 or 20 carbon atoms.

The viscosity depressants of formula (3) are well known compositions andinclude compositions containing different R and R groups. For example,the R groups can be methyl, while the R groups can be phenyl and/ orbeta-cyanoethyl. Furthermore, within the scope of the definition ofpolydiorganosiloxanes useful in this invention are copolymers of varioustypes of diorganosiloxane units, such as silanol chain-stoppedcopolymers of dirnethylsiloxane units, diphenylsiloxane units andmethylphenylsiloxane units or, for example, copolymers ofdimethylsiloxane units, methylphenylsiloxane units and methylvinylsiloxane units. Preferably at least 50% of the R and R groups ofthe silanol chain-stopped polydiorganosiloxanes are methyl groups. Theviscosity depressant of formula (3) has a viscosity that generallyvaries from 10 to centistokes at 25 C. when p varies from 2 to 46 and,more preferably, from 15 to 50 centistokes at 25 C. where p varies from3 to 9. Preferably, the value of p varies from 3 to 9 in formula (3) butgenerally p may vary from 2 to 46. Generally, when p varies from 2 to46, the viscosity depressant functions elfectively throughout the entirerange of the other ingredients, since it will have a viscosity thatvaries from 10 to 100 centistokes at 25 C. Above this viscosity rangethe viscosity depressant does not lower the viscosity of the compositionsufficiently below the above viscosity range. Below this range, theviscosity depressant is a silane which is unstable and too reactive tofunction as a viscosity depressant in the composition. The viscositydepressant is most effective when p preferably varies from 3 to 9 andits viscosity correspondingly varies from 15 to 50 centistokes at 25 C.It is quite important that for the viscosity depressant to function asdesired that generally it should have 1% to 20% by weight of hydroxylcontent based on the weight of the viscosity depressant fluid andpreferably 5 to 15% by weight. Generally, for the viscosity depressantto be effective it must be used at a concentration of 0.3 to 20 partsbased on 100 parts of the basic silanol diorganopolysiloxane andpreferably at a concentration of l to 5 arts.

In formula (3), the hydrocarbyl, halohydrocarbyl and cyano lower alkylradicals represented by R and R can be selected from the same group asthose listed above for R and R The base silanol chain-stopped materialsuseful in the practice of the present invention described as preferablyhaving a viscosity of from about 1,000 to 90,000 centistokes andgenerally having a viscosity of 1,000 to 10,000,- 000 centistokes at 25C., are well known in the silicone RTV art and have the formula,

I H VO where R and R are independently selected from the class ofhydrocarbyl radicals, halohydrocarbyl radicals and cyano lower alkylradicals and preferably of such radicals of up to 8 carbon atoms. The Rand R radicals are defined and are selected from the same radicals asthe R and R radicals. In addition, q is a whole number that graduallyvaries from 300 to 5,260 and preferably from 370 to 1,350. Basesilanol-stopped gums having a viscosity of 10,000,000 centistokes can beused. Such materials can also contain minor amounts, e.g., up to aboutof monoorganosiloxane units such as monoalkylsiloxane units, e.g.,monomethylsiloxane units and monophenylsiloxane units. The technologyinvolved in incorporating monoalkylsiloxane units into RTV compositionsis disclosed in US. Pat. 3,382,205 of Beers (1968), which is herebyincorporated into the present application by reference. The silanolchain-stopped materials may also contain triorganosiloxane units, suchas trialkylsiloxane units, e.g., trimethylsiloxane units,tributylsiloxane units and triphenylsiloxane units. The silanolchain-stopped materials may also contain t-alkoxysilane units, e.g.,t-butoxysiloxane units, t-pentoxysiloxane units and t-amyloxysiloxaneunits. Effective results can be obtained if sufficient t-alkoxysi-loxaneis utilized in combination with the silanol-terminatedpolydiorganosiloxane to provide a polymer having a ratio oft-alkoxysiloxane units to silanol of 0.05 to 0.9 and preferably 0.2 to0.8 tert-alkoxydialkylsiloxy units per silanol. Many of thet-alkoxysiloxanes useful as part of the silanol chain-stopped materialsare described and claimed in US. Pat. 3,438,930 of Beers which issuedApr. 15, 1969 and is assigned to the General Electric Company, thedisclosure of which is expressly incorporated herein by reference.

Examples of silanes useful in the RTV compositions of this invention ascross-linking agents include the following:

CH Si (OCH 3 CH Si(OCH CH 3 (CH SiOCH Si(OCH 4 CH CH CH CH CH CH CH CHSi(OCH 3 CF OH Si OCH 3 NCCH CH Si(OCH 3 (CH Si (OCH CH CH CH 3 io IExamples of preferable titanium chelate catalysts of formula (2) usefulin the RTV compositions of this in- I o C CH CH OCH CH ,0 c c CH CH Tl 2s CH o o c Other examples are readily apparent from the description ofthe substituents which may be present on the titanium.

The titanium chelate catalysts are generally utilized at a concentrationof 0.01 to parts based on 100 parts of the based silanol-stopped polymerof formula (4) and preferably at a concentration of 0.5 to 1 part.Although the preferred titanium chelate catalysts in the presentinvention are the ones within the scope of formula (2), nevertheless,other types of titanium chelate catalysts can be used in the alkoxy typeof RTV of the present case. In all cases such titanium catalysts causeundesirable viscosity increases which are assuaged by the viscositydepressant of formula (3) as set forth in the composition of the presentcase.

The preferred alkanedioxy titanium chelates of the present invention canbe prepared first by adding a beta-dicarbonyl compound such as abeta-diketone or a beta-ketoester to a titanium ortho ester of a loweraliphatic alcohol. This reaction is represented by the followingequation:

Preferably, two moles of the beta-dicarbonyl compound are used per moleof titanium compound. Toluene is the preferred solvent, preferably, inthe amount of from .5 parts to 10 parts per part of alkyl titanate. Inthe above formula, R is a lower alkyl radical having 1 to 8 carbon atomsand R R and X are as previously defined. It is preferred thatstoichiometric quantities of reactants be employed as this avoids theproblem of removing unreactive starting material.

The second step of the preparation involves the reaction of the dialkoxytitanium chelate preparation of which is described above with analkanediol. This reaction is illustrated by the following equation:

In the above formulas, R and R are as previously defined. Again, it ispreferred that the quantities of reactants be stoichiometric. If anexcess of the alkanediol is employed only one of the hydroxyl groups ofsome of the diol will react with the titanium by alkoxy interchange toform hydroxyalkoxy-substituted titanates. In addition to the desiredproduct, the alkoxy exchange reaction employing the diol also can leadto the formation of minor amounts of polymeric materials where onehydroxy of the diol will react with one titanium chelate and the secondhydroxy will react with the second titanium chelate to form a dimer.Trimer and tetramer formation can also occur in this manner. The use oflarge quantities of solvent such as from two to twenty parts of tolueneper part of the chemlated dialkyl titanates tends to diminish trimer andtetramer formation.

It is preferred that when the dicarbonyl compound is a lower alkyl esterof acetoacetic acid that the temperature be maintained below 70 C. Thepreferred dicarbonyl compound is a lower alkyl ester of acetoaceticacid. The alkyl group can be straight chain or branched. The preferredgroup of acetoacetates include methylacetoacetate, ethylacetoacetate,propylacetoacetate, isobutylacetoacetate, pentylacetoacetate,hexylacetoacetate, heptylacetoacetate, and octylacetoacetate. Thepreferred acetoacetate is ethylacetoacetate. It is also preferred that Rbe an isopropyl radical as this via alkoxy interchange producesisopropyl alcohol. The isopropyl alcohol can then be azeotroped offusing toluene as the azeotroping agent in both of the above-describedreactions.

The use of a solvent is not necessary but is preferred. Solvents otherthan toluene which can be employed include benzene, xylene, hexane orany other of the well known solvents useful for the azeotrop-ic removalof formed alcohol from solution.

The RTV compositions of the present invention are prepared by simplyadmixing one or more of the silanes of formula (1), having an average ofat least about 2.01 silicon-bonded alkoxy radical per silicon atom, thetitanium chelate of formula (2), and the viscosity, depressant offormula (3) with the base silanol chain stopped polydiorganosiloxane offormula (4). The components are preferably at room temperature duringmixing. Since the silanes tend to hydroxlyze upon contact with moisture,care should be exercised to exclude moisture during the addition of thesilane to the silanol chain-stopped polydiorganosiloxane. Likewise, careshould be taken that the mixture is maintained under substantiallyanhydrous conditions if it is desired to store the mixture for anextended period of time prior to converson of the composition to thecured state. On the other hand, if it is desired to permit the mixtureto cure immediately upon admixture, no special precautions are necessaryand the components can be mixed and placed in the form or shape in whichit is desired for the composition to be cured.

The amount of the silane of formula (I) admixed with the base silanolchain-stopped polydiorganosiloxane can vary within wide limits. However,for best results, it is preferred to add an excess of one mole of thesilane per mole of silanol groups in the base silanol chain-stoppedpolydiorganosiloxanes of formula (4). Satisfactory curing can beobtained, for example, with from 1.0 to moles of the silane per mole ofsilanol groups in the polydiorganosiloxane. No particular detriment issuffered from using more than 10 moles of the silane per mole of thebase polydiorganosiloxane except for a more resinous product beingformed and slowing down the cure. Sufficient viscosity depressant offormula (3) is added to provide from about one mole of OH contributed bythe viscosity depressant per mole of titanate to a molar ratio of onemole of OH per 10 moles of titanate. The preferred range is a ratio ofabout 1:2 to 1:4. The temperature at which the composition is admixed isnot critical and a room temperature addition is usually employed.

The admixture can be carried out in the presence of an inert solvent(that is, a solvent which will not react with the silanol or alkoxygroups on the silicon). Suitable solvents include hydrocarbon such asbenzene, toluene, xylene, or petroleum ethers; halogenated solvents suchas perchloroethylene or chlorobenzene and organic ethers such asdiethylether and dibutylether; ketones such as methylisobutylketone andfluid hydroxylfree polysiloxanes. The presence of a solvent isparticularly advantageous when the sillanol chain-stoppedpolydiorganosiloxane is a high molecular weight gum. The solvent reducesthe overall viscosity of the composition and facilitates cure. The RTVcompositions may be kept in the solvent until they are to be used. Thisis particularly valuable when a gummy composition is to be employed incoating applications.

The RTV compositions of this invention are stable in the absence ofmoisture. Consequently, they can be stored for prolonged periods of timewithout deleterious effect. During this period of storage no significantchange occurs in the physical properties of the RTV compositions. Thisis of particular importance from a commercial standpoint, since itassures that once an RTV composition is prepared with a certainconsistency and cure time that neither will change significantly uponstorage. Storage stability is one of the characteristics which makes thecompositions of this invention particularly valuable as one componentroom temperature vulcanizing compositions.

A wide choice of components is available in the preparation of the RTVcompositions of the present invention. In general, the particularcomponents employed are a function of the properties desired in thecured silicone rubber. Thus, with a particular silane, some variation inthe properties of the cured silicone rubber are obtained by varying themolecular weight (as measured by viscosity) of the silanol chain-stoppedpolydiorganosiloxane. For a given system, as the viscosity of thesilanol chainstopped starting material increases, the elongation of thecured rubber increases. On the other hand, with a lower viscositymaterial, the cure is tighter so that the cured rubber has a lowerelongation and increased hardness.

RTV compositions prepared by mixing the novel viscosity depressant, atitanium catalyst and the silane with the base silanol chain-stoppedpolydiorganosiloxanes can be used without further modification in manySealing, caulking or coating applications by merely placing thecompositions in the desired place and permitting them to cure uponexposure to the moisture present in the atmosphere. Upon exposure ofsuch compositions to atmospheric moisture, even after storage for timesas long as two years or more, a skin will form on the compositionsshortly after exposure and cure to the rubbery state will occur withinone to three days, all at room temperature. The time required for theformation of such skin can vary from a minimum of about one hour to amaximum of about eight hours.

It is often desirable to modiy the RTV compositions of the presentinvention by the addition of various materials which act as extenders orwhich change various properties such as cure rate and color. Forexample, if it is desired to reduce the time required for complete cure,the composition can be modified by the incorporation of a minor amountof carboxylic acid salt, alkoxide, hydroxide, and/or oxide of a metalranging from lead to manganese, inclusive, in the electromotive seriesof metals. The particular metals included are lead, tin, nickel, cobalt,iron, cadmium, chromium, zinc and manganese with tin being preferredUThecarboxylic acids from which the salts of these metals are derived can bemonocarboxylic acids or dicarboxylic acids and the metallic salts can beeither soluble or insoluble in the silanol chain-stoppedpolydiorganosiloxane. Preferably, the salts employed are soluble in thesilanol chainstopped polydiorganosiloxane since this facilitates theuniform dispersion of the salt in the reaction mixture.

Illustrative of metal salts which can be employed are, for example, zincnaphthenate, lead naphthenate, cobalt naphthenate, iron Z-ethylhexoate,cobalt octoate, zinc octoate, lead octoate, chromium octoate, and tinoctoate. Operative metals salts include those in which the metallic ioncontains a hydrocarbon substituent such as, for example,carbomethoxyphenyl tin tris-uberate, isobutyl tin triceroate,cyclohexenyl lead triactotinate, dimethyl tin di'butyrate, basicdimethyl tin oleate, dibutyl tin diacetate, dibutyl tin dilaurate,divinyl tin diacetate, dibutyl tin dibenzoate, dibutyl tin dioctoate,dibutyl tin maleate, dibutyl tin adipate, diisoamyl tinbistrichlorobenzoate, diphenyl lead diformate, dicyclopentyl leadbis-monochloroacetate, dibenzyl lead di-Z-pentanoate, diallyl leaddi-Z-hexenoate, triethyl tin tartrate, tributyl tin acetate, triphenyltin acetate, tricyclohexyl tin acrylate, tritolyl tin terephthalate,tri-n-propyl lead acetate, tri-stearyl lead succinate, tri-naphthyl leadp-methylbenzoate, tris-phenyl lead cycloliexenyl acetate, triphenyl leadethylmalonate, etc.

The amount of the metal salt of the organic carboxylic acid which can beemployed is a function of the increased rate of curing desired so thatany amount of such salt up to the maximum effective amount forincreasing the cure rate can be employed. In general, no particularbenefit is derived from employing more than about 5% by weight of suchmetal salt based on the weight of the silanol chain-stoppedpolydiorganosiloxane. Preferably, where such metal salt is employed, itis present in an amount equal to from about 0.01% to 2.0% by weight,based on the weight of the polydiorganosiloxane.

Metal chelates such as those disclosed in US. Pats. 3,334,067 and3,065,194 can also be used in the RTV compositions of this invention inamounts from about 0.01 part to about 10 parts based on parts of thebase silanol chain-stopped polydiorganosiloxane of formula (4), althoughthe titanium chelate catalysts of formula (2) are preferred.

The alkoxides second catalyst or co-catalyst which can be used in thepractice of the present invention include dibutyl tin dimethoxide,dimethyl tin diethoxde, dibutyl tin dibutoxide, tin tetraisopropoxide,tin tetramethoxide, and tributyl tin methoxide.

The RTV compositions of the present invention can also be varied by theincorporation of various extenders or fillers. Illustrative of the manyfillers which can be employed with the compositions of the presentinvention are titanium dioxide, lithopone, zinc oxide, zirconiumsilicate, silica aerogel, iron oxide, diatomaceous earth, calciumcarbonate, fumed silica, silazane treated silica, precipitated silica,octamethylcyclotetrasiloxane treated silica, glass fibers, magnesiumoxide, chromic oxide, zirconium oxide, aluminum oxide, crushed quartz,calcined clay, asbestos, carbon, graphite, cork, cotton, syntheticfibers, etc. Silazane treated silica fillers such as those disclosed andclaimed in application Ser. No. 789,352 of Smith, filed Jan. 6, 1969,now U.S. Pat. 3,635,743, are particularly suitable for use in the RTVcompositions of the present invention, they are generally employed inamounts from about to about 200 parts filler, per 100 parts of the basesilanol chain-stopped polydiorganosiloxane.

In addition to the modification of the RTV compositions of the presentinvention by addition of metal salt, cure accelerators and fillers,these compositions can also be modified by the incorporation of variousflame retardants, stabilizing agents and plasticizers such as siloxanefluids. Suitable flame retardants include antimony ox ide, variouspolyhalogenated hydrocarbons and organic sulfonates.

Where the compositions of the present invention contain components otherthan the silane, the titanium chelate catalyst, the viscosity depressingadditive and the base polydiorganosiloxane, the various ingredients canbe added in any desired order. However, for ease of manufacturing, it isoften convenient to form a blend or mixture of all of the components ofthe room temperature vulcanizing organopolysiloxane except the silane offormula (1) and the titanium chelate catalyst, to then remove moisturefrom the resulting mixture by maintaining the mixture under vacuum andthereafter to add the silane and the titanium chelate catalyst prior topackaging of the composition in containers protected from moisture.

The RTV compositions of the present invention are particularly adaptedfor caulking and sealing applications where adhesion to various surfacesis important. For example, these materials are useful in householdcaulking applications and industrial applications such as on buildings,factories, automotive equipment and in applications where adhesion tomasonry, glass, plastic, metal and wood is required.

The silanes represented by formula (1) are well known in the art and aredescribed, for example, in U.S. Pat. 2,843,555 of Berridge.

When the silane is employed as a cross-linking agent, m has a value of 1and the preferred silane is CH Si(OCH When it is desired to have a chainextending agent employed in combination with the cross-linking agent, mhas a value of 2, resulting in the silane being difunctional. Thepreferred difunctional silane is (CH Si(OCH The presence of a chainextending agent results in a final cured product having a higher degreeof elasticity. The same result would be obtained if a higher molecularWeight silanol-stopped fluid were used, However, the use of such ahigher molecular weight silanol-stopped fluid would result in a muchhigher viscosity of the curable composition resulting in difliculties inhandling the extremely viscous material.

When it is desired to improve the modulus of elasticity, a silane offormula (1), wherein m has a value of 3, is incorporated into the RTVcomposition. The preferred silane for this application is (CH SiOCH Theuse of this monofunctional silane chain terminating unit in combinationwith the cross-linking and optionally chain extending silanes discussedabove, not only results in a higher modulus of elasticity but in manyinstances also improves the adhesion of the cured compositions to asubstrate.

The preferred base silanol chain-stopped polydiorganosiloxanes offormula (2) to be used in combination with the silane cross-linkingagent described above are silanol chain-stopped polydiorganosiloxaneshaving a viscosity in the range of preferably about 1,000 centistokes to90,000

centistokes at 25 C. The preferred base polydiorganosiloxanes arepolydimethylsiloxanes and can contain some trimethylsiloxy groups. Thepresence of tertiary alkoxy groups such as t-butoxy groups also improvesthe adhesion of the RTVs of the present invention to particularsubstrates.

Generally speaking, in the preferred embodiment of the presentinvention, R is an alkyl radical of not more than 4 carbon atoms, R isan alkyl radical of not more than 4 carbon atoms, R is hydrogen, R is analkyl radical of not more than 4 carbon atoms and at least 50% of thegroups represented by R and R are methyl radicals, the remainder phenyl.

The preferred silanes of formula (1) used in the RTV compositionsdescribed in the present invention contain on the average of from 2.05to 3 silicon-bonded alkoxy groups per silane when a fluid containing twosilanol terminal groups is employed. If the number of alkoxy groups wereto be two this would merely result in a build-up of chain length.Average in this situation means the total number of silicon bondedalkoxy groups divided by the total number of silane molecules used inthe RTV composition. The number, of course, can drop below two when thesilanol-stopped polydiorganosiloxane contains more than two silanolgroups per molecule. This occurs when there is chain branching in thepolydiorganosiloxane and no chain stopping with nonreactive groups suchas t-butoxy groups, alkyl groups or trimethylsilyl groups.

As stated previously, the preferred RTV compositions of the presentinvention can include a second catalyst such as a tin catalyst, i.e.,dibutyl tin dimethoxide. The preferred second catalyst of the titaniumchelate catalysts of the present invention include dialkyl tindialkoxide such as dibutyl tin dimethoxide, dimethyl tin diethoxide,dimethyl tin dimethoxide and other preferred components include hydroxyalkyl tin salts such as hydroxy dimethyl tin oleate and dihydroxymethyltin oleate. Solubilized dibutyl tin oxide is also a very effectivesecond catalyst. This material is available from Argus Chemical Corp.,633 Court Street, Brooklyn, N.Y. 11231.

As stated previously, the preferred RTV compositions of the presentinvention also include fillers. The most preferred of which is thesilazane treated silica. filler disclosed and claimed in applicationSer. No. 789,352 of Smith, filed Jan. 6, 1969, now U.S. Pat. 3,635,743.The fillers are preferably used in amounts from about 10 to about partsof filler, per 100 parts of the silanol chain-stoppedpolydiorganosiloxane.

The silazane treated filler can be prepared by the following procedure.A fumed silica filler is contacted with ammonia for about 1% hours at 25C. with agitation. Hexamethyldisilazane is added to the treated fillerin an amount of about 20 parts per 100 parts of treated filler and themixture is heated to about C. for about 2 hours. Water in an amount ofabout one part by weight is added to the mixture and heating iscontinued at 130 C. for an additional hour. The treated silica filler isthen purged with N at 130 C. until the NH content is 50 p.p.m.

EXAMPLE 1 A base compound was prepared containing 100 parts of a 3000centipoise silanol-terminated polydimethylsiloxane fluid correspondingto the formula,

I CH3 SIiO l CH: [455 HO H 7.0 parts of a fumed silica which had beentreated with octamethylcyclotetrasiloxane, the filler had a surface areaof 200 square meters per gram, 11.0 parts of hexamethyldisilazanetreated fumed silica having a surface area of 200 square meters per gramand 2.5 parts of a low molecular weight silanol-terminatedpolydimethylsiloxane containing 6.2 weight percent hydroxyl groups.

New

Control sealant Shore A hardness 45 45 Tensile, p.s.i 390 370Elongation, perce 230 250 Tear, lbs./inch...- 18 21 Application rateusing a V Simco nozzle at 90 p.s.i.

pressure at maximum viscosity 11. 4 181 EXAMPLE 2 A base compound wasprepared by mixing 70 parts of a 30,000 centipoise silanol-terminatedpolydimethylsiloxane, 30 parts of a 3000 centipoise partially t-butoxyand silanol-terminated polydimethylsiloxane having an OH to t-butoxyratio of 2.76, 2.7 parts of a silanol-terminated, low molecular weightpolydimethylsiloxane having a hydroxyl content of 6.2 weight percent,and 27 parts of hexamethyl-disilazane treated fumed silica having asurface area of 200 square meters per gram.

To 100 parts of this base compound was added 4.3 parts ofmethyltrimethoxysilane, 0.75 parts of 1,3- propanedioxytitaniumbis(ethylacetoacetate), 0.75 parts of1,3,5-tris-trimethoxysilylpropylisocyanurate as an adhesion promoter,and 0.05 parts of dibutyltindimethoxide. The properties of the newsealant described in this example and the control without thesilanol-terminated low molecular weight polydimethylsiloxane having ahydroxyl content of 6.2 weight percent are shown in the following table:

New

Control sealant Shore A hardness 48 46 Tensile, p.s.i 830 815Elongation, percent 620 670 Tear, lbs./inch 125 150 Application rate(using a V "Simco nozzle at 90 p .i. 72 15 pressure at maximumviscosity) EXAMPLE 3 The base compound was prepared containing 100 partsof a 3000 centipoise silanol-terminated polydimethylsiloxane fluidcorresponding to the formula:

l CH3 has siloxane containing 6.2 Weight percent hydroxyl groups.

The properties of the new sealant described in this example and thecontrol are shown in the following table:

New

Control sealant Shore A hardness 39 37 380 350 pressure at maximumviscosity) 20 314 I claim:

1. A fluid composition stable under substantially anhydrous conditionsand curable to an elastic solid in the presence of moisture consistingessentially of a base silanol chain-stopped polydiorganosiloxane havingthe formula,

l H OSi OH where R and R are independently selected from the classconsisting of hydrocarbyl, halohydrocarbyl and cyano lower alkyl and qvaries from 300 to 5,260, a silane represented by the formula:

0.01 to 10 parts based on parts of the base polydiorganosiloxane of atitanium chelate catalyst and 0.3 to 20 parts based on 100 parts of thepolydiorganosiloxane of a viscosity depressant of the formula:

I HO sio H wherein R is a radical having not more than about 8 carbonatoms selected from the group consisting of hydrocar-byl,halohydrocarbyl, and cyano lower alkyl, R is a radical not having notmore than about 8 carbon atoms selected from the group consisting ofhydrocarbyl, halohydrocarbyl and cyano lower alkyl, R and R are eachorganic radica s of not more than 8 carbon atoms selected from the groupconsisting of hydrocarbyl, halohydrocarbyl and cyano lower alkyl, m hasa value of 0 to 3 and an average value based upon the total amount ofsilane in the composition of 0 to 1.99, and p has a value of 2 to 46.

2. The composition of Claim 1 further characterized by at least 50% ofthe total number of R and R groups being methyl radicals.

3. The composition of Claim 2 further characterized by the remaining Rand R groups being phenyl radicals.

4. The composition of Claim 1 wherein the titanium chelate catalyst hasthe formula,

where R is a radical selected from the class consisting of hydrogen,hydrocarbyl having not more than about 8 carbon atoms, carboxyalkyl andhalohydrocarbyl having not more than about 8 carbon atoms and the totalnumber of carbon atoms in the R and R substituted alkanedioxy radical isnot more than about 18, R is a radical having not more than about 8carbon atoms selected from the class consisting of hydrocarbyl,halohydrocarbyl and cyano lower alkyl, R is selected from the same classas R and halo, cyano, nitro, carboxy ester, acyl and hydrocarbylsubstituted by halo, cyano, nitro, carboxy ester and acyl, R is selectedfrom the class consisting of hydrogen, hydrocarbyl having not more thanabout 8 carbon atoms, halohydrocarbyl having not more than about 8carbon atoms, acyl having not more than about 8 carbon atoms, and takentogether with R forms together with carbon atoms to which they areattached cyclic hydrocarbon substituents of not more than 12 carbonatoms and chloro, nitro, acyl, cyano and carboxy ester substitutedcyclic hydrocarbon substituents; X is a radical having up to 20 carbonatoms selected from the class consisting of hydrocarbyl,halohydrocarbyl, cyanoalkyl, alkoxy, haoalkoxy, cyanoalkoxy and amino, ais a whole number that varies from 0 t0 8 and such that when a is zerothe moieties are bonded to each other in a cyclic fashion.

5. The composition of Claim 4 further characterized by R, R and R beingalkyl radicals and R and R being hydrogen.

6. The composition of Claim 4 further characterized by R, R and R beingmethyl radicals, X being OC H and having a value of 1.

7. The composition of Claim 4 further characterized by R and R being H.

8. The composition of Claim 4 further characterized by R, R R and Xbeing methyl radicals and R and R being H.

9. The composition of Claim 4 further characterized by the mixturecomprising a base silanol chain-stopped polydiorganosiloxane having aviscosity from about 1,000 to about 90,000 centistokes,

CH SI (0CH CII-l'a HO SIiO H CH3 p and CH Si (0on CH O O C/OCHZCH3 2 ICH2 T1 CH \CH- 0 o c 2 and I CH

where p is a number that varies from about 3 to about 9.

References Cited UNITED STATES PATENTS 3,607,972 9/1971 Kiles et al260-465 G 3,689,454 9/1972 Smith et a1 26046.5 G 3,334,067 8/1967Weyenberg 260-465 G MELVYN I. MARQUIS, Primary Examiner US. Cl. X.R.

117--124 F, 132 ES, 138.8 R; 260-9, 18 S, 32.8 SB, 33.6 SB, 33.8 SB,46.5 G

0.01 TO 10 PARTS BASED ON 100 PARTS OF THE BASE POLYDIORGANOSILAXANE OFA TITANIUM CHELATE CATALYST AND 0.3 TO 20 PARTS BASED ON 100 PARTS OFTHE POLYDIORGANOSILOXANE OF A VISCOSITY DEPRESSANT OF THE FORMULA:
 1. AFLUID COMPOSITION STABLE UNDER SUBSTANTIALLY ANHYDROUS CONDITIONS ANDCURABLE TO AN ELASTIC SOLID IN THE PRESENCE OF MOISTURE CONSISTINGESSENTIALLY OF A BASE SILANOL CHAIN-STOPPED POLYDIORGANOSILOXANE HAVINGTHE FORMULA,